Salmonella tymphimurium strains TA-98, TA-100, TA-1535 are being used to detect ongoing chemicals of interest for mutagenicity. A series of cyclic hydrazides which are analogs of nitrosamines are being tested for mutagenicity for comparison with mutagenic and non-mutagenic nitrosamine counterparts. N-aminomorpholine, N-aminopiperidine, N-aminohomopiperidine, 1-amino-4-methylpiperazine, N-aminopyrrolidine, and 1,4-diaminopiperazine hydrate were all mutagenic, producing only base substitution mutations in the presence and absence of rat liver S-9. As a rule, more activity was seen in the absence of S-9.